Hollow golf club head

ABSTRACT

A golf club head of the present invention includes a face portion having an impact surface that impacts a golf ball and is made from a metallic material, and a crown portion, a heel portion, a sole portion, and the toe portion that are adjacent to the face portion. In at least two portions from among the crown portion, the heel portion, the sole portion, and the toe portion, at least one from among dissimilar metallic materials that differ from the metallic material of the impact surface and fiber reinforced plastic materials is used in regions along ends that are adjacent to the face portion, within a range of 30 mm from the adjacent ends. Thereby, the golf club has a structure that easily deforms with respect to golf ball impacts, and the face portion deforms more than conventional face portions. The coeffecient of restitution of a struck golf ball therefore increases, the initial velocity of the golf ball increases, and the carry distance increases.

TECHNICAL FIELD

The present invention relates to a hollow golf clubhead having a faceportion in which an impact surface that impacts a golf ball is made froma metallic material, a crown portion that is adjacent to the faceportion, a heel portion, a sole portion, and a toe portion.

BACKGROUND ART

It has become known in recent years that the coefficient of restitutionof a golf ball can be increased in a metallic hollow golf club head byusing a titanium alloy or the like for an impact surface that impacts agolf ball, and in addition, by making the thickness of a face memberthat forms the impact surface thinner, or by making portions of ajoining edge, where the face member is joined to other members such as acrown member and a sole member, partially thinner.

JP 10-155943 A discloses a hollow golf club head in which a thin portionis provided in an inner circumferential edge of a golf ball impactsurface. Elastic deformation of the impact surface during golf ballimpacts is thus promoted, thus increasing the restitution coefficient ofthe struck golf ball which results in an increase of the carry distanceof the golf ball.

However, if the face member is made thinner in its entirety orpartially, the rigidity of the face member itself decreases, and themechanical strength with respect to an impact force during golf ballimpacts decreases. Accordingly, there is a limit to how thin the facemember can be made. A problem therefore exists in that the coefficientof restitution of a struck golf ball cannot be increased further by theabove-described method of making the face member thinner in its entiretyor partially.

DISCLOSURE OF THE INVENTION

An object of the present invention is thus to provide a hollow golf clubhead capable of increasing the coefficient of restitution of a struckgolf ball to increase the carry distance of the golf ball, by a methodthat differs completely from the method described above of increasingthe coefficient of restitution by changing the thickness of a facemember.

In order to achieve the above object, according to the presentinvention, there is provided a hollow golf club head, including a faceportion having an impact surface that impacts a golf ball and is madefrom a metallic material, and a crown portion, a heel portion, a soleportion, and a toe portion that are adjacent to the face portion,characterized in that, in at least two portions from among the crownportion, the heel portion, the sole portion, and the toe portion, atleast one material of dissimilar metallic material that differ from themetallic material and fiber reinforced plastic material is used inregions along edges that are adjacent to the face portion, within arange of 30 mm from the adjacent edges.

Further, the present invention may be adapted such that the at least twoportions from among the crown portion, the heel portion, the soleportion, and the toe portion are divided into two portions along edgesthat are adjacent to the face portion, in regions within a range of 30mm from the adjacent edges, each of the at least two portions having afirst member that extends to the face portion, and a second member as aportion other than the first member, and joining portions are formed byjoining members made from fiber reinforced plastics, the joining membersoverlapping the first member and the second member respectively to join.

Further, the present invention may be adapted such that the at least twoportions from among the crown portion, the heel portion, the soleportion, and the toe portion are divided into two portions along edgesthat are adjacent to the face portion, in regions within a range of 30mm from the adjacent edges, each of the at least two portions having afirst member that extends to the face portion, and a second member madefrom fiber reinforced plastics, and joining portions are formed at whichthe second members overlap with and join to the first members.

Here, it is preferable the at least two portions from among the crownportion, the heel portion, the sole portion, and the toe portion havecutout portions within a range of 30 mm from edges that are adjacent tothe face portion, along the adjacent edges, and at least one of thereinforced plastic material and the dissimilar metallic material beprovided to close the cutout portions.

Further, it is preferable that at least one of the fiber reinforcedplastic material and the dissimilar metallic material be provided whilebonded with members around the cutout portions.

Further, it is preferable that the dissimilar metallic material be alloymaterial selected from the group consisting of titanium alloy, magnesiumalloy, stainless steel alloy, and aluminum alloy.

Further, it is preferable that an elastic modulus of fibers of the fiberreinforced plastic materials be less than 27×10³ kg-f/mm².

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front view schematically showing a hollow golf club headthat is an embodiment of a hollow golf club head of the presentinvention, FIG. 1B is a side view of the golf club head shown in FIG. 1Aas seen from a face portion side, and FIG. 1C is a bottom view of thegolf club head shown in FIG. 1A as seen from a sole portion side.

FIG. 2 is a cross sectional view of the golf club head taken along aline A-A of FIG. 1A as seen from the direction of arrows A, and

FIGS. 3A and 3B are diagrams for explaining where cutout portions areprovided in a toe portion and a heel portion, respectively.

FIG. 4A is a side view of a hollow golf club head that is an embodimentof a hollow golf club head of the present invention as seen from a heelside,

FIG. 4B is a top view of the golf club head shown in FIG. 4A as seenfrom a crown side,

FIG. 4C is a front view of the golf club head shown in FIG. 4A as seenfrom a face side.

FIG. 5 is a cross sectional view of the golf club head taken along aline B-B of FIG. 4B as seen from the direction of arrows B.

FIG. 6A is a side view of a hollow golf club head that is an embodimentof a hollow golf club head of the present invention as seen from a heelside,

FIG. 6B is an upper surface view of the golf club head shown in FIG. 6Aas seen from a crown side, and FIG. 6C is a front view of the golf clubhead shown in FIG. 6A as seen from a face side.

FIG. 7 is a cross sectional view of the golf club head taken along aline C-C of FIG. 6B as seen from the direction of arrows C.

FIG. 8 is an explanatory diagram for explaining an orientation angle ofa laminate composite material, and

FIG. 9 is an explanatory diagram for explaining the thickness of thegolf club head shown in FIG. 4.

FIG. 10A is a side view of a hollow golf club head that is an embodimentof a hollow golf club head of the present invention as seen from a heelside,

FIG. 10B is a top view of the golf club head shown in FIG. 10A as seenfrom a crown side, and

FIG. 10C is a front view of the golf club head shown in FIG. 10A as seenfrom a face side.

FIG. 11 is a cross sectional view of the golf club head taken along aline E-E of FIG. 10B as seen from the direction of arrows E.

BEST MODES FOR CARRYING OUT THE INVENTION

A hollow golf club head of the present invention is explained below indetail based on preferred embodiments shown in the appended drawings.

First Embodiment

FIG. 1A is a front view schematically showing a hollow golf club head(hereinafter referred to simply as a golf club head) 10 that is a firstembodiment of a hollow golf club head of the present invention. FIG. 1Bis a side view of the golf club head 10 as seen from a face portionside, and FIG. 1C is a bottom view of the golf club head 10 as seen froma sole portion side.

The golf club head 10 is configured having a face portion 12, in whichan impact surface that strikes a golf ball is made from a metallicmaterial, a crown portion 14 that forms an upper surface of the golfclub head 10, a neck portion 16 that has a shaft insertion hole 15 intowhich a golf club shaft is inserted, a heel portion 18 that is a sideportion connected along an edge of the crown portion 14 and ispositioned on the neck portion 16 side, a toe portion 20 that ispositioned on a side opposite to the neck portion 16 sandwiching theface portion 12, and a sole portion 22 which is connected along an edgeof the heel portion 18 and the toe portion 20 and disposed opposite thecrown portion 14, forming a bottom surface of the golf club head 10.

The crown portion 14, the heel portion 18, the toe portion 20, and thesole portion 22 are adjacent to the face portion 12.

A side portion is formed with the heel portion 18 and the toe portion 20by at least one side member.

It should be noted that the face portion 12, the crown portion 14, thesole portion 22, and the side portion may be formed by manufacturingmembers corresponding to the respective portion and then bonding thosemembers together into an integral structure through welding, by using anadhesive, or the like. Alternatively, members corresponding to at leasttwo of the face portion 12, the crown portion 14, the sole portion 22,and the side portion may be manufactured integrally, and then thosemembers may be bonded together through welding, by using an adhesive, orthe like to form an integral structure. Furthermore, the crown portion14 and the sole portion 22 may each be formed such that a portion of thecorresponding member and remaining portions thereof are manufacturedseparately from each other and then bonded together through welding, byusing an adhesive, or the like to form an integral structure.

In any case, there are no specific limitations placed on a method ofmanufacture of the gold club head 10.

The face portion 12, the heel portion 18, and the toe portion 20 areeach configured by a metal alloy selected from the group consisting oftitanium alloys, magnesium alloys, stainless steel alloys, and aluminumalloys.

The crown portion 14 is structured by: a crown main body member 14 awhich is configured by a metal alloy selected from the group consistingof titanium alloys, magnesium alloys, stainless steel alloys, andaluminum alloys, and has a slit-like cutout portion 14 b, and a closingmember 14 c that engages with the slit-like cutout portion 14 b and isbonded to the crown main body member 14 a in the periphery of the cutoutportion 14 b, closing the cutout portion 14 b.

Further, the sole portion 22 is structured by: a sole main body member22 a which is configured by a metal alloy selected from the groupconsisting of titanium alloys, magnesium alloys, stainless steel alloys,and aluminum alloys; and a closing member 22 c which engages with aslit-like cutout portion 22 b provided to the sole main body member 22 aand which is bonded to the sole main body member 22 a in the peripheryof the cutout portion 22 b.

It should be noted that both of the cutout portions 14 b and 22 b areadapted to have large cutout widths in both ends of the cutout portions14 b and 22 b so that excess stress does not concentrate at the ends.

The closing members 14 c and 22 c are composite materials formed bylaminating a plurality of layers of a fiber reinforced plastic materialin which fibers are arranged in a predetermined direction. The fiberreinforced plastic material is formed by impregnating reinforcing fiberssuch as carbon fibers, glass fibers, or aramid fibers into a matrixresin such as an epoxy resin, an unsaturated polyester resin, or a vinylester resin. It should be noted that it is preferable that thereinforcing fibers have an elastic modulus that is less than 27×10³kg-f/mm².

Further, used for the closing members 14 c and 22 c are materials thathave a lower flexural rigidity than that of the metallic material usedin the face portion 12, preferably materials that have a lower Young'smodulus than that of the metallic material used in the face portion 12.The term flexural rigidity as used herein means flexural rigidity in acondition that a flexure force is applied in an out-of-plane directionalong a cut line of the crown portion taken along a plane perpendicularto the impact surface of the face portion.

FIG. 2 is a cross sectional view of the golf club head 10 taken along aline A-A of FIG. 1A as seen from the direction of arrows A.

The closing member 14 c is disposed along an edge of the crown portion14, adjacent to the face portion 12, in a region of the crown portion 14within a range of 30 mm from the edge of the crown portion 14 which isadjacent to the face portion 12. The closing member 22 c is disposedalong an edge of the sole portion 22, adjacent to the face portion 12,in a region of the sole portion 22 that is within a range of 30 mm fromthe edge of the sole portion 22 which is adjacent to the face portion12.

The closing members 14 c and 22 c are provided along the edges that areadjacent to the face portion 12, in the regions that are within 30 mmfrom the edges, because deformation during impact of the face portion 12can be effectively made larger to increase the coefficient ofrestitution of a struck golf ball, thus increasing the carry distance ofthe golf ball. That is, by using this type of configuration, thecoefficient of restitution of a golf ball can be increased, and thecarry distance of the golf ball can be increased, without making thethickness of the face portion 12 thinner. This is shown in embodimentsof the present invention described hereinafter. It should be noted thatit is preferable to set the length of the closing member 14 c that isdisposed along the edge of the crown portion 14, adjacent to the faceportion 12, to be from 20 to 50 mm in order to effectively demonstratethe effects described above.

It should also be noted that, although fiber reinforced plasticmaterials are used in the embodiment described above in the closingmember 14 c of the cutout portion 14 b of the crown portion 14, and inthe closing member 22 c of the cutout portion 22 b of the sole portion22, dissimilar metallic materials that differ from the metallic materialused in the face portion 12 may also be used as the closing members. Inthis case, a fiber reinforced plastic may also be used in one of thecrown portion 14 and the sole portion 22, while a dissimilar metallicmaterial is used in the other.

In this case as well, the dissimilar metallic material used is amaterial having a lower flexural rigidity than that of the metallicmaterial used in the face portion 12, and preferably is a materialhaving a lower Young's modulus.

For cases where metal having a single component is used, the term“dissimilar metallic material” means different type of component. Inaddition, when alloy is used, the term “dissimilar metallic material”means alloy where the sum of smaller composition ratios selected amongtwo respective composition ratios of each shared component with thecompared alloy is less than 20%. For example, when comparing a 6-4titanium alloy (Ti:Al:V=90:6:4) and a 15-5-3 titanium alloy(Ti:Mo:Zr:Al=77:15:5:3), the sum of composition ratios described abovebecomes 80% (=77+3), and therefore the 6-4 titanium alloy and the 15-5-3titanium alloy cannot be referred to as the dissimilar metallicmaterials. On the other hand, the 6-4 titanium alloy and a magnesiumalloy having a magnesium composition ratio equal to or greater than 80%can be referred to as the dissimilar metallic materials.

Furthermore, in addition to the crown portion 14 and the sole portion22, cutout portions may also be formed in the heel portion 18 and thetoe portion 20. Dissimilar metallic materials that differ from themetallic material used in the face portion 12, and the fiber reinforcedplastic materials described above, may be used to close the cutoutportions. In this case, as shown in FIGS. 3A and 3B, the cutout portionsare formed adjacent to the face portion 12, in regions within a range of30 mm from edges that are adjacent to the face portion 12, alongcontours of the toe portion 20 and the heel portion 18. Portions of theheel portion 18 and the toe portion 20 therefore have the cutoutportions within a region that is 30 mm from the edges that are adjacentto the face portion 12, along the adjacent edges. Closing members areemployed to close the cutout portions. In this case it is preferablethat the length of the closing members disposed along the edges that areadjacent to the face portion 12 be set to 10 to 20 mm.

In the present invention, the fiber reinforced plastic material and thedissimilar metallic material that differs from the metallic materialused in the face portion 12 are used in at least two portions from amongthe crown portion, the sole portion, the heel portion, and the toeportion.

It should be noted that the edge adjacent to the face portion 12 is aregion whose radius of curvature is equal to or less than half of theradius of curvature in the vicinity of the center of the face portion12, namely a portion where the radius of curvature changes substantiallydiscontinuously.

The hollow golf club head of the present invention is thus one in whichat least one material of fiber reinforced plastic material anddissimilar metallic material that differ from the metallic material usedin the face portion, is used along an edge that is adjacent to the faceportion of the golf club head, in a region within a range of 30 mm fromthe edge, in at least two portions from among the crown portion, theheel portion, the sole portion, and the toe portion of the golf clubhead. This provides a structure in which, in addition to the faceportion, the at least two portions from among the crown portion the heelportion, the sole portion, and the toe portion easily deform withrespect to golf ball impacts. The face portion thus deforms more than aconventional face portion. The coefficient of restitution of a struckgolf ball can therefore increase, the initial velocity of the golf ballcan increase, and the carry distance can increase.

There are no specific limitations placed on a method of providing theclosing members 14 c and 22 c of the golf club head 10 in the embodimentdescribed above, and any method may be used. For example, each of mainbody members such as a crown main body member and a sole member may bemanufactured with two separate main body portion members having cutoutportions in boundaries thereof. After disposing closing members in theposition of the cutout portions formed by the two manufactured main bodyportion members, the closing members and the main body portion membersin the periphery of the closing members may be bonded together by usingan adhesive. The two main body portion members may also be bonded byusing welding or an adhesive.

The carry distance of a golf ball was measured by using the hollow golfclub head of the present invention, and effects of the present inventionwere investigated.

The golf club head shown in FIGS. 1A to 1C was manufactured as thehollow golf club head of the present invention. The golf club head wasmanufactured by using a laminated composite material made from a carbonfiber reinforced plastic material in the closing member 14 c of thecrown portion 14 and the closing member 22 c of the sole portion 22,with a member made from the 15-5-3 titanium alloy employed in the faceportion, and members made from the 6-4 titanium alloy in other members(Example 1).

Used for the carbon fiber reinforced plastic material were carbon fiberswith an elastic modulus equal to or less than 27×10³ kg-f/mm². It shouldbe noted that the configuration of the composite material is one havinga four layer structure in which four layers are laminated alternately atan orientation angle of ±45°. The term “orientation angle” as used heremeans an orientation direction of the carbon fibers, taking a golf ballstriking direction as a reference direction.

In addition, a golf club was manufactured by forming cutout portions inthe crown portion 14, the heel portion 18, the toe portion 20, and theheel portion 22 along edges that are adjacent to the face portion 12, inregions within a range of 30 mm from the edges. Composite materialssimilar to those of Example 1 were used as closing members for thecutout portions, and the same titanium alloy as that used in Example 1was used in other portions (Example 2).

Further, a golf club head was manufactured by using a magnesium alloywhich has a composition ratio for magnesium equal to or greater than 80%for the closing member 14 c of the crown portion 14 and the closingmember 22 c of the sole portion 22 of FIGS. 1A to 1C. The same titaniumalloy as that used in Example 1 was used in other members (Example3).The magnesium alloy is used as dissimilar metallic material with respectto the titanium alloy.

In addition, a golf club was manufactured by forming cutout portions inthe crown portion 14, the heel portion 18, the toe portion 20, and theheel portion 22 along edges that are adjacent to the face portion 12, inregions within a range of 30 mm from the edges. A magnesium alloysimilar to that of Example 3 was used as closing members for the cutoutportions, and the same titanium alloy as that used in Example 1 was usedin other portions (Example 4).

It should be noted that the flexure rigidity for the closing members ismade lower than the flexural rigidity of the face portion in Embodiments1 to 4.

Furthermore, a hollow golf club head made from a single alloy configuredby a titanium alloy similar to that used in Examples 1 to 4 was alsomanufactured as a comparative example.

Golf clubs were manufactured by attaching golf club shafts to themanufactured golf club heads, and in addition, providing grip portionsto the golf club shafts.

Measurement of the carry distance was performed by test hitting golfballs with the manufactured golf clubs swung by a Miya Shot Robo IV madeby Miyamae Co., Ltd., under conditions of a head speed of 40 m/s.

The carry distances were collected as indexes taking the carry distanceof the comparative example as 100, and results shown in Table 1 belowwere obtained. It should be noted that a higher index shows golf ballcarry distance longer.

The notation “FRP” in Table 1 below means a carbon fiber reinforcedplastic material.

TABLE 1 Closing Carry Closing member position member distance Example 1Crown portion, sole FRP 107 portion Example 2 Crown portion, sole FRP112 portion, heel portion, toe portion Example 3 Crown portion, soleMagnesium 105 portion alloy Example 4 Crown portion, sole Magnesium 110portion, heel portion, toe alloy portion Comparative — — 100 Example

It can be understood from Table 1 above that the carry distances for allof the golf clubs that use the golf club heads of Examples 1 to 4 arelonger than the carry distance of the Comparative Example.

Second Embodiment

FIG. 4A is a side view, as seen from a heel side, that shows a schematicof a hollow golf club head (hereinafter referred to simply as a golfclub head 110) according to a second embodiment of a hollow golf clubhead of the present invention. FIG. 4B is a top view of the golf clubhead 110 shown in FIG. 4A as seen from a crown side, and FIG. 4C is afront view of the golf club head 110 shown in FIG. 4A as seen from aface side.

The golf club head 110 is configured by a face portion 112 having animpact surface for striking a golf ball and which is made from ametallic material, a crown portion 114 that forms an upper surface ofthe golf club head 110, a neck portion 116 that has a shaft insertionhole 115 into which a golf club shaft is inserted, a heel portion 118that is a side portion connected along an edge of the crown portion 114and is positioned on the neck portion 116 side, a toe portion 120 thatis positioned on a side opposite that of the neck portion 116,sandwiching the face portion 112, and a sole portion 122 that isconnected along an edge of the heel portion 118 and the toe portion 120,and is disposed opposite the crown portion 114, forming a bottom surfaceof the golf club head 110.

The heel portion 118, the toe portion 120, the sole portion 122, and thecrown portion 114 are adjacent to the face portion 112.

A side portion is formed for the heel portion 118 and the toe portion120 by at least one side member. The face portion 112, the heel portion118, and the toe portion 120 are made from titanium alloys, but may alsobe made from alloys selected from the group consisting of titaniumalloys, magnesium alloys, stainless steel alloys, and aluminum alloys.

The crown portion 114 and the sole portion 122 are made from titaniumalloys, and may also be made from alloy materials selected from thegroup consisting of titanium alloys, magnesium alloys, stainless steelalloys, and aluminum alloys, or fiber reinforced plastic materials(FRPs).

At least two portions from among the crown portion, the heel portion,the sole portion, and the toe portion are each divided into face sidesand back sides.

In this embodiment, the crown portion and the sole portion are selectedas the two portions. As shown in FIG. 4, a joining line 130 made from aresin is taken as a boundary, thus dividing the crown portion 114 into aface side crown portion and a back side crown portion. A joining line132 is taken as a boundary, thus dividing the sole portion into a faceside sole portion and a back side sole portion. The joining lines 130and 132 are positioned along edges that are adjacent to the face portion112, and within a range of 30 mm from the adjacent edges. It should benoted that the whole joining lines 130 and 132 do not need to bedisposed along the edges adjoining the face portion 112, and containedwithin a range of 30 mm from the adjoining edges. The total length ofthe joining lines existing in at least two portions should be equal toor greater than 40 mm.

The members used in the crown portion 114 and in the sole portion 122,which are each divided into two portions along the joining lines, arebonded by an adhesive to joining portions 140 (or 144) and 142,respectively, shown in FIG. 5A (or FIG. 5B). The face side and the backside are thus integrated. The joining portions are configured by carbonfiber reinforced plastic materials in which carbon fibers areimpregnated in a matrix resin as reinforcing fibers. It should be notedthat the joining portions may also be configured by using fiberreinforced plastic materials in which reinforcing fibers such as carbonfibers, glass fibers, or aramid fibers are impregnated into a matrixresin such as an epoxy resin, an unsaturated polyester resin, or a vinylester resin.

In this embodiment, the crown portion and the sole portion are eachdivided into two portions, and the divided members are integratedthrough the joining portions. Accordingly, the golf club head 110becomes a structure that easily deforms with respect to golf ballimpacts. The face portion therefore deforms more than a conventionalface portion. The coefficient of restitution of a struck golf ball canbe increased, the initial velocity of the golf ball can be increased,and the carry distance can be increased.

FIG. 5A is a cross sectional view of the golf club head 110 taken alonga line B-B as seen from the direction of arrows B shown in FIG. 4B.

Among the crown portion and the sole portion that are each divided intotwo portions, a member that configures the face side is referred to asthe face side member 112, and members that configure the back side arereferred to as the back sidemembers 114 and 122. In the embodiment shownin FIGS. 5A and 5B, both the face side member and the back side membersare configured by titanium alloys, separated along the joining lines 130and 132. The joining lines are resins embedded in gaps between the faceside member and sole side members. However, the joining lines are notlimited to this configuration, and may also be embedded in fiberreinforced plastic material (FRP) for example. Furthermore, the width ofthe gaps is set to 1 mm. The gaps are provided in order to make astructure that easily deforms with respect to golf ball impacts, andtheir width may be suitably set.

The joining portions 140 and 142 are each configured by one joiningmaterial, and are each made from a carbon fiber reinforced plastic. Thelength of the joining portion 140 is taken as F₁, the length of aportion that bonds to the face side crown portion is taken as G₁, andthe length of a portion that bonds to the back side crown portion istaken as H₁. The entire length F₁ of the joining portion may be from 15mm to 80 mm. Further, the length G₁ of the face side joining portion ispreferably from 8 mm to30 mm, more preferably from 12 mm to 20 mm. Thelength H₁ of the back side joining portion is preferably from 5 mm to 40mm, more preferably from 5 mm to 30 mm, and additionally preferably from5 mm to 20 mm.

It should be noted that the entire length and the joining lengths of thejoining portion 142 are repectivle similar to those of the joiningportion 140.

FIG. 5B is a cross sectional view of the golf club head 110 taken alongthe line B-B as seen from the direction of the arrows B shown in FIG.4B, and shows a variation of the joining portion 140. With FIG. 5B, aportion of the joining portion 144 that is bonded to the face side iscurved and bonded to the face portion 112. The joining portion of theface side thus contacts not only the crown portion, but also the faceportion. The joining portion 142 may also similarly contact the faceportion. However, in this case as well, an entire length F₂ of thejoining portion is from 15 mm to 80 mm, preferably from 5 to 20 mm.

Third Embodiment

FIG. 6A is a side view, as seen from a heel side, that shows a schematicof a hollow golf club head (hereinafter referred to simply as a golfclub head 160) that is a third embodiment of a hollow golf club head ofthe present invention. FIG. 6B is a top view of the golf club head shownin FIG. 6A as seen from a crown side, and FIG. 6C is a front view of thegolf club head shown in FIG. 6A as seen from a face side.

In the second embodiment the same metallic material (titanium alloy) isused in the crown portion 114 and the sole portion 122 as that used inthe face portion 112. In the third embodiment, however, dissimilarmetallic materials that differ from the material used in the faceportion are used. It should be noted that portions that are the same asthose of the second embodiment mode use the same appended referencenumerals, and explanations thereof are omitted.

For cases where metal having a single component is used, the term“dissimilar metallic material” means different type of component. Inaddition, when alloy is used, the term “dissimilar metallic material”means alloy where the sum of smaller composition ratios selected amongtwo respective composition ratios of each shared component with thecompared alloy is less than 20%.

The hollow golf club head of the present invention is configured so thatat least two portions from among a crown portion 124, the heel portion118, a sole portion 126, and the toe portion 120 are divided into twoportions at a region along edges that are adjacent to the face portion,within a range of 30 mm from the adjacent edges, each having a firstmember that extends to the face portion 112 and another second member.

In this embodiment, the crown portion 124 and the sole portion 126 areselected as the portions divided in two. As shown in FIG. 7, the crownportion 124 is divided into a face side crown portion and a back sidecrown portion, with the joining line 130 made from a resin as aboundary, and the sole portion 126 is divided into a face side soleportion and a back side sole portion with the joining line 132 made froma resin as a boundary.

In addition, joining portions are formed as shown in FIGS. 7A and 7B bythe joining members 140 (or 144) and 142 that overlap with the firstmember and the second member to join. The joining members are made fromfiber reinforced plastics. The hollow golf club head of the presentinvention thus has a structure that easily deforms with respect to golfball impacts. There is more deformation than with a conventional faceportion, and therefore the coefficient of restitution of a struck golfball can be increased, the initial velocity of the golf ball can beincreased, and the carry distance can be increased.

FIG. 7A is a cross sectional view of the golf club head shown in FIG. 6Btaken along a line C-C as seen from the direction of arrows C. With thegolf club head 110 shown in FIG. 5A, the joining portion is configuredby one joining member, but with the golf club head 160 shown in FIG. 7A,the joining portion 140 is configured as a portion of the back sidemember 124, and is made from a carbon fiber reinforced plastic.

FIG. 7B is a cross sectional view of the golf club head shown in FIG. 7Ataken along a line C-C as seen from the direction of arrows C, and is analternative example of the joining portion 140. In FIG. 7B, a portion ofthe joining portion 144 that is bonded to the face side is bent and isbonded to the face portion. The joining portion of the face side thusmay also be joined to the face portion, not only the crown portion.However, in this example as well the entire length F₂ of the joiningportion is from 15 to 80 mm. Further, the joining portion 142 may alsosimilarly contact the face portion.

The hollow golf club head of the present invention is one in which atleast two portions from among the crown portion, the heel portion, thesole portion, and the toe portion are respectively divided into tworegions along edges that are adjacent to the face portion, within arange of 30 mm from the adjacent edges, each having the first memberthat extends to the face portion, and the second member made from afiber reinforced plastic. In addition, the second members of the hollowgolf club are overlapping with the first members to join to, forming thejoining portions. The hollow golf club head of the present inventiontherefore has a structure that easily deforms with respect to golf ballimpacts. The face portions deforms more than a conventional faceportion, and therefore the coefficient of restitution of a struck golfball can be increased, the initial velocity of the golf ball can beincreased, and the carry distance can be increased.

Effects of the present invention were investigated by measuringdurability and restitution characteristics using the hollow golf clubhead of the present invention.

The golf club heads shown in FIGS. 4A to 4C were manufactured as thehollow golf club heads of the present invention.

The crown portion and the sole portion were selected as divided portionsas shown in FIGS. 4A to 4C, and a titanium alloy (Ti alloy) was used inthe first member and the second member of the crown portion and the soleportion, as shown in FIG. 5A. The titanium alloy used was composed of15% V by weight, 3% Cr by weight, 3% Al by weight, 3% Sn by weight, withTi in the remainder. Further, gaps between the first members and thesecond members were filled and closed by using a resin.

A composite material including a laminated carbon fiber reinforcedplastic material (CFRP) was used in the joining portions. The carbonfiber reinforced plastic material was one in which the carbon fibers hadan elastic modulus of 24×10³ kg-f/mm², a fiber density of 160 g/m², anda resin content of 38%. It should be noted that the composite materialhad a six layer configuration in which layers were laminated alternatelyat an orientation angle of ±45°. The term “orientation angle” as usedhere means the orientation direction of the carbon fibers, taking a golfball strike direction D as a reference direction as shown in FIG. 8.

Members made from a 15-5-3 titanium alloy were used as the face members.

In addition, as shown in FIG. 9, the thickness of the first members ofthe crown portion and the sole portion was taken as t₁, and thethickness of joining members made from the carbon fiber reinforcedplastic material in the joining portions was taken as t₂. As shown inFIG. 5A, the length of the face side joining portion was taken as G, andthe length of the back side joining portion was taken as H. Theseparameters were set as shown in Table 2 below, and Experimental Examples1 to 20 were manufactured. It should be noted that, in the presentinvention, it is preferable that the thickness t₁ be set to 0.5 to 2.0mm, and that the thickness t₂ be set to 0.5 to 1.5 mm. It is morepreferable that the thickness t₁ be set to 0.8 to 1.8 mm, and that thethickness t₂ be set to 0.8 to 1.2 mm.

The thickness t₁ of the first members, the thickness t₂ of the joiningmembers made from carbon fiber reinforced plastic material, the length Gof the face side joining portion, and the length H of the back sidejoining portion may be limited within a range of ±20% from the center ofthe face width in the toe to heel direction in any cross sectionthereof, taking the face width as 100%. In defining the face width, anend portion of the toe is defined as a location that projects furthestout toward the toe side under a normal address position of the golf clubhead. An end portion of the heel is defined as a location that is 16 mmabove the ground surface under the normal address position. It ispreferable that the cross section be perpendicular with respect to thesurface of the face portion and the ground surface.

Establishing the term “the normal address position” as used here meansto place the golf club head 1 according to its lie angle, and set thecenter axis of the golf club shaft and the leading edge of the faceportion of the golf club head to be parallel with each other as seenfrom vertically above the ground surface, that is, so that the faceangle becomes zero degrees. The term “set according to lie angle” meansto place the golf club head 1 so that gaps between the round surface ofthe sole portion that forms a bottom surface of the golf club head andthe ground surface are substantially equal at the toe side and the heelside. For cases where the round surface of the sole portion is unclear,the golf club head 1 may also be set so that scorelines formed in thesurface of the face portion become parallel with the ground surface.Further, for cases where the round surface of the sole portion isunclear and where it is difficult to determine whether or not the scorelines are parallel with the reference surface due to the score lines notbeing straight or the like, the lie angle may be set so that the lieangle (degrees)=(100−club length (inches)). For example, when a golfclub length is 44 inches, the lie angle may be set to 100−44=56°.

The club length is measured here by a measurement method specified bythe Japan Golf Gear Association. A club measurer II manufactured byKamoshita Seikoujyo K.K. can be given as a measurement unit.

Taking Experimental Example 1 as a conventional example, neither thecrown portion nor the sole portion was divided in the conventionalexample, and only a titanium alloy was used. The thickness of the crownportion and the sole portion was 1.7 mm. In Experimental Examples 2 to11, the thickness t₁ of the first members and the thickness t₂ of thejoining portions were changed while holding the lengths G and H of thejoining portions constant. In Experimental Examples 12 to 20, thelengths G and H of the joining portions were changed while holding thethickness t₁ of the first members and the thickness t₂ of the joiningportions constant.

Golf clubs were manufactured by attaching a golf club shaft modelTRX-DUO M40 (product name) manufactured by Yokohama Rubber Co., Ltd. tothe manufactured golf club heads, and the experiments shown below wereperformed. The length of the golf clubs were each set to 45 inches.

Further, TRX (product name) balls manufactured by Yokohama Rubber Co.were used as golf balls in each of the experiments.

For durability, golf balls were impacted to a center portion of the faceportion of each of the golf club heads of the experimental examples atvelocity of 50 m/sec by using an air cannon tester, and the number ofball strikes up to failure was measured. In this case, the strength ofeach of the embodiments is expressed as an index, taking the number ofball strikes up to failure of the conventional example (embodiment 1) as100.

For the restitution characteristics, evaluation was performed by using acoefficient of restitution for each embodiment measured based on the“Procedure for Measuring the Velocity Ratio of a Club Head forConformance to Rule 4-1e, Appendix II Revision 2 Feb. 8, 1999”prescribed by the USGA (United States Golf Association). In this case,the restitution of each of the embodiments is expressed as an index,taking the coefficient of restitution of the conventional example as100.

The point totals in Table 2 below are values found by adding indexes ofthe durability and the restitution characteristics together. The pointtotal for the conventional example (Experimental Example 1) becomes 200,and becomes larger the better the durability and the restitutioncharacteristics become.

TABLE 2 t₁ t₂ thickness t₁ thickness t₂ G H Point (mm) material (mm)material (mm) (mm) Durability Restitution total Experimental Example 11.7 Ti alloy — — — — 100 100 200 Experimental Example 2 1.5 Ti alloy 0.6CFRP 15 10 152 106 258 Experimental Example 3 1.2 Ti alloy 0.8 CFRP 1510 152 110 262 Experimental Example 4 1.0 Ti alloy 1.0 CFRP 15 10 150113 263 Experimental Example 5 0.7 Ti alloy 1.2 CFRP 15 10 145 113 258Experimental Example 6 0.3 Ti alloy 1.4 CFRP 15 10 135 115 250Experimental Example 7 2.2 Ti alloy 0.5 CFRP 15 10 156 93 249Experimental Example 8 1.8 Ti alloy 0.3 CFRP 15 10 150 99 249Experimental Example 9 0.7 Ti alloy 1.8 CFRP 15 10 153 97 250Experimental Example 10 2.2 Ti alloy 0.3 CFRP 15 10 152 93 245Experimental Example 11 0.3 Ti alloy 2.0 CFRP 15 10 147 98 245Experimental Example 12 1.2 Ti alloy 0.8 CFRP 5 10 116 121 237Experimental Example 13 1.2 Ti alloy 0.8 CFRP 15 2 124 115 239Experimental Example 14 1.2 Ti alloy 0.8 CFRP 5 2 92 140 232Experimental Example 15 1.2 Ti alloy 0.8 CFRP 36 10 156 82 238Experimental Example 16 1.2 Ti alloy 0.8 CFRP 15 25 155 86 241Experimental Example 17 1.2 Ti alloy 0.8 CFRP 36 25 161 74 235Experimental Example 18 1.2 Ti alloy 0.8 CFRP 10 25 140 98 238Experimental Example 19 1.2 Ti alloy 0.8 CFRP 18 10 153 106 259Experimental Example 20 1.2 Ti alloy 0.8 CFRP 25 10 154 97 251

As can be understood from Experimental Examples 2 to 11 shown in Table2, each of the Experimental Examples 2 to 11 has a larger point totalthan the conventional example (Experimental Example 1). In particular,the point total for Experimental Examples 2 to 5 is large, and inaddition it can be understood that the point totals of ExperimentalExamples 3 and 4 are largest.

It can therefore be said that it is preferable that the thickness t₁ befrom 0.5 to 2.0 mm and the thickness t₂ be from 0.5 to 1.5 mm, and thatit is more preferable that the thickness t₁ be from 0.8 to 1.8 mm andthe thickness t₂ be from 0.8 to 1.2 mm.

Further, comparing Experimental Examples 12 to 20 shown in Table 2 withExperimental Example 3, which has the identical thickness t₁ and theidentical thickness t₂, the point totals for Experimental Examples 13and 16, in which the length G of the joining portion is equal to orgreater than 8 mm, are larger than the point total for ExperimentalExample 14, in which the length G is equal to or less than 8 mm and thelength H of the joining portion is equal to or less than 5 mm. The pointtotals for Experimental Examples 12 and 15, in which the length H isequal to or greater than 5 mm, are larger than the point total forExperimental Example 14, in which the length G is equal to or less than8 mm and the length H is equal to or less than 5 mm. The point total forExperimental Example 3, in which the length G is equal to or less than20 mm, is larger than the point total of Experimental Example 20, inwhich the length G is equal to or greater than 20 mm. The point totalfor Experimental Example 3, in which the length H is equal to or lessthan 20 mm, is greater than the point total for Experimental Example 16,in which the length H is equal to or greater than 20 mm.

It is preferable that the length of G be from 8 mm to 30 mm, and morepreferably from 12 to 20 mm.

It is preferable that the length H be from 5 mm to 40 mm, morepreferably from 5 mm to 30 mm, and even more preferably from 5 mm to 20mm.

Fourth Embodiment

FIG. 10A is a side view of a hollow golf club head of the presentinvention (hereinafter referred to simply as a golf club head 210) asseen from a heel side, FIG. 10B is an upper surface view of the golfclub head shown in FIG. 10A as seen from a crown side, and FIG. 10C is afront view of the golf club head shown in FIG. 10A as seen from a faceside.

The golf club head 210 is configured to include a face portion 212, inwhich an impact surface that impacts a golf ball is made from a metallicmaterial, a crown portion 214 that forms an upper surface of the golfclub head 210, a neck portion 216 that has a shaft insertion hole 215into which a golf club shaft is inserted, a heel portion 218 that is aside portion connected along an edge of the crown portion 214 and isdisposed on the neck portion 216 side, a toe portion 220 that isdisposed on a side opposite the neck portion 216, sandwiching the faceportion 212, and a sole portion 222 that is connected along edges of theheel portion 218 and the toe portion 220, forming a bottom surface ofthe golf club head 210 disposed opposing the crown portion 214.

The heel portion 218, the toe portion 220, the sole portion 222, and thecrown portion 214 are adjacent to the face portion 212.

The heel portion 218 and the toe portion 220 form a side portion here byat least one side member. The face portion 212, the heel portion 218,and the toe portion 220 are made from a titanium alloy, but may also beconfigured from an alloy selected from the group consisting of titaniumalloys, magnesium alloys, stainless steel alloys, and aluminum alloys.

Portions of the crown portion 214 and the sole portion 222 are made fromtitanium alloys, but may also be configured from an alloy materialselected from the group consisting of titanium alloys, magnesium alloys,stainles ssteel alloys, and aluminum alloys, or from a fiber reinforcedplastic (FRP).

In this embodiment mode, the crown portion, the sole portion, and theside portion (the heel portion 218 and the toe portion 220) are selectedas at least two portions of the claimed invention. As shown in FIG. 10,the crown portion is divided into a face side crown portion and a backside crown portion, one edge of the face side crown portion beingadjacent to the face portion 212, with another edge 230 within a rangeof 30 mm from the one edge adjacent to the face portion 212. The soleportion is also divided into a face side and a back side, similar to thecrown portion, with one edge adjacent to the face surface, and anotheredge 233 within a range of 30 mm from the one edge adjacent to the facesurface. The side portion made from the heel portion 218 and the toeportion 220 is also similarly divided into a face side and a back side,with one edge of each adjacent to the face portion 212, and other edges236 and 237 within a range of 30 mm from the one edges.

FIG. 11A is a cross sectional view of the golf club head shown in FIG.10B taken along a line E-E as seen from the direction of arrows E.

The face side crown portion and the back side crown portion are joinedmutually overlapping, and the face side sole portion and the back sidesole portion are joined mutually overlapping. In addition, the face sideheel portion and the back side heel portion are joined mutuallyoverlapping, and the face side toe portion and the back side toe portionare similarly joined mutually overlapping.

It is preferable that a joining portion length G₂ shown in FIG. 11A beset from 8 mm to 30 mm, more preferably from 12 mm to 20 mm.

In this embodiment, the face side crown portion is configured by thesame titanium alloy as that of the face portion, but may also beconfigured by an alloy material chosen from the group consisting oftitanium alloys, magnesium alloys, stainless steel alloys, and aluminumalloys. Further, the back side crown portion is configured by a carbonfiber reinforced plastic, but may also be configured by a fiberreinforced plastic material in which reinforcing fibers such as carbonfibers, glass fibers, or aramid fibers are impregnated in a matrix resinsuch as an epoxy resin, an unsaturated polyester resin, or a vinyl esterresin. It should be noted that the sole portion and the side portion(toe portion and heel portion) are similar.

The face side crown portion and the back side crown portion, the faceside sole portion and the back side sole portion, and the face-side sideportion (the toe portion and the heel portion) and the sole-side sideportion (the toe portion and the heel portion) are mutually bonded by anadhesive or a resin film, respectively. Epoxies, urethanes, acrylics,and cyanoacrylate resins are examples of a type of the adhesive.Further, thermoplastic resin films such as polyurethane resins, nylonresins, denatured nylon resins, polyethylene terephthalate resins,polyvinyl chloride resins, polycarbonate resins, polyvinylidene chlorideresins, ethyl cellulose resins, and acetylcellulose resins are examplesof the resin film.

It should be noted that it is preferable that the resin film used have ahigh compatibility with prepreg matrix resins. For example, for caseswhere an epoxy resin or the like is used as a matrix resin, polyurethaneresins, denatured nylon resins, and the like are suitable as the resinfilm. It is preferable that the thickness of the resin film be set from0.02 to 0.2 mm.

FIG. 11B is a cross sectional view of the golf club head shown in FIG.10B taken along a line E-E as seen from the direction of arrows E, andshows a variation of the joining portion. In FIG. 11B, a portion of thejoining portion that bonds to the face side crown portion is bent, andthe back side crown portion is bonded to the face portion. The joiningportion of the back side crown portion thus also contacts the faceportion, not only the face side crown portion. However, in this case itis preferable that a length G₃ of the face side joining portion be from8 mm to 30 mm, more preferably from 12 mm to 20 mm. Similarly, thejoining portion of the back side sole portion may also contact the faceportion, not only the face side sole portion. A length G₄ of the soleside joining portion may also contact the face portion at this point. Inaddition, the side portion (the toe portion and the heel portion) mayalso contact the face portion.

The hollow golf club head of the present invention is one in which atleast two portions from among the crown portion, the heel portion, thesole portion, and the toe portion are divided into two portions alongedges that are adjacent to the face portion, in regions within a rangeof 30 mm from the adjacent edges, having the first member that extendsto the face portion and the second member that is made from a fiberreinforced plastic. In addition, the second member of the hollow golfclub head is joined overlapping with the first member, forming thejoining portion. The hollow golf club head of the present inventiontherefore has a structure that easily deforms with respect to golf ballimpacts. The face portion deforms more than that of conventional faceportions, and therefore the coefficient of restitution of a golf ballcan be increased, the initial velocity of the golf ball can beincreased, and the carry distance can be increased.

The hollow golf club of the present invention is explained in detailabove, but the present invention is not limited to the embodimentsdescribed above. Various types of improvements and changes may of coursebe made within a range that does not deviate from the gist of thepresent invention.

INDUSTRIAL APPLICABILITY

At least two portions from among the crown portion, the heel portion,the sole portion, and the toe portion of the hollow golf club head ofthe present invention are along edges that are adjacent to the faceportion, in regions within a range of 30 mm from the adjacent edges, anduse at least one of a reinforced plastic material and a dissimilar metalthat differs from a metallic material that configures the face portion.The flexural rigidity in these portions can therefore be made lower thanthe flexural rigidity of the face portion, and deformation of the faceportion at a golf ball impact point becomes large. The coefficient of astruck golf ball can thus be increased, and the golf ball carry distancecan be increased.

1. A hollow golf club head, comprising a face portion having an impactsurface that impacts a golf ball and is made from a metallic material,and a crown portion, a heel portion, a sole portion, and a toe portionthat are adjacent to the face portion, wherein, in at least two portionsfrom among the crown portion, the heel portion, the sole portion, andthe toe portion, at least one material of dissimilar metallic materialthat differs from the metallic material and a fiber reinforced plasticmaterial is used in regions along edges that are adjacent to the faceportion, within a range of 30 mm from the adjacent edges, wherein saidat least two portions from among the crown portion, the heel portion,the sole portion, and the toe portion are divided into two portionsalong the edges that are adjacent to the face portion, in regions withina range of 30 mm from the adjacent edges, each of said at least twoportions having a first member that extends to the face portion and asecond member as a portion other than the first member, wherein joiningportions are formed by joining members made from a fiber reinforcedplastic material, each joining member joining the first member and thesecond member of each of said at least two portions, said first membersnot overlapping said second members, and wherein a thickness t₁ of thefirst member which is joined by the joining member ranges from 0.5 to2.0 mm, and a thickness t₂ of the joining member which joins to thesecond member ranges from 0.5 to 1.5 mm.
 2. The hollow golf club headaccording to claim 1, wherein the dissimilar metallic material is analloy material selected from the group consisting of titanium alloy,magnesium alloy, stainless steel alloy, and aluminum alloy.
 3. Thehollow golf club head according to claim 1, wherein an elastic modulusof fibers of the fiber reinforced plastic material is less than 27×10³kg-f/mm².
 4. The hollow golf club head according to claim 1, wherein thefirst member and the second member respectively are joined to thejoining member with an adhesive.